A diesel engine may be stopped and then started when ambient temperatures are cold. The diesel engine may be difficult to start and it may exhibit combustion stability levels that are less than is desired when it is started at low ambient temperatures because low cylinder temperatures may make it more difficult for air-fuel mixtures in engine cylinders to reach ignition temperature. Glow plugs and grid heaters may be utilized to increase temperature within an engine's cylinders, but the engine may still be difficult to start. Further, to reduce engine starting times, more expensive ceramic tip glow plugs may have to be deployed in the engine. As such, the glow plugs and grid heater may increase system cost significantly. Therefore, it may be desirable to provide a way of improving cold engine so that the engine may be started without glow plugs or with lower cost glow plugs.
The inventors herein have recognized the above-mentioned disadvantages and have developed an engine operating method, comprising: adjusting operation of an electric machine that is coupled to a compressor via a controller to generate a predetermined desired temperature in an engine or a predetermined desired pressure in the engine, the predetermined desired temperature and the predetermined desired pressure changing as a function of engine speed and engine load.
By adjusting output of an electric machine that is coupled to a compressor to generate a predetermined temperature or pressure in an engine, it may be possible to operate an engine at lower engine temperatures without assistance from glow plugs and/or grid heaters. Further, because the electric machine is adjusted to provide a predetermined temperature or pressure instead of simply maximizing boost pressure, efficiency of operating the engine may improve. Adjusting the electric machine to provide the predetermined temperature or pressure also helps to ensure that the temperature or pressure in the engine is sufficient to support combustion within the engine and improve combustion stability after the engine is started.
The present description may provide several advantages. In particular, the approach may improve engine starting. In addition, the approach may be applied to a wide variety of engine configurations. Further, the approach may provide different temperatures in an engine for different operating conditions so that engine efficiency may be improved during cold engine starting.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.